Method of forming metal nitride film by chemical vapor deposition and method of forming metal contact and capacitor of semiconductor device using the same

ABSTRACT

A method of forming a metal nitride film using chemical vapor deposition (CVD), and a method of forming a metal contact and a semiconductor capacitor of a semiconductor device using the same, are provided. The method of forming a metal nitride film using chemical vapor deposition (CVD) in which a metal source and a nitrogen source are used as a precursor, includes the steps of inserting a semiconductor substrate into a deposition chamber, flowing the metal source into the deposition chamber, removing the metal source remaining in the deposition chamber by cutting off the inflow of the metal source and flowing a purge gas into the deposition chamber, cutting off the purge gas and flowing the nitrogen source into the deposition chamber to react with the metal source adsorbed on the semiconductor substrate, and removing the nitrogen source remaining in the deposition chamber by cutting off the inflow of the nitrogen source and flowing the purge gas into the deposition chamber. Accordingly, the metal nitride film having low resistivity and a low content of Cl even with excellent step coverage can be formed at a temperature of 500° C. or lower, and a semiconductor capacitor having excellent leakage current characteristics can be manufactured. Also, a deposition speed, approximately 20 A/cycle, is suitable for mass production.

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/156,724, filed Sep. 18, 1998, entitled METHOD OF FORMINGMETAL NITRIDE FILM CHEMICAL VAPOR DEPOSITION AND METHOD OF FORMING METALCONTACT OF SEMICONDUCTOR DEVICE USING THE SAMEMETHOD OF FORMING METALNITRIDE FILM CHEMICAL VAPOR DEPOSITION AND METHOD OF FORMING METALCONTACT OF SEMICONDUCTOR DEVICE USING THE SAME, now U.S. Pat. No.6,197,683.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of fabricating semiconductordevices, and more particularly, to a method of forming a metal nitridefilm by chemical vapor deposition (CVD) where a metal source and anitrogen source are used as a precursor, and a method of forming a metalcontact and a capacitor of a semiconductor device using the abovemethod.

2. Description of the Related Art

A barrier metal layer, which prevents mutual diffusion or chemicalreaction between different materials, is indispensable to stabilize thecontact interfaces of semiconductor devices. In general, a metal nitridesuch as TiN, TaN or WN has been widely used as the barrier metal layerof semiconductor devices. Here, TiN is a representative example amongthe above metal nitrides.

However, when the metal nitride film such as TiN is fabricated bysputtering, its application to highly integrated semiconductor devicesis not appropriate, due to low step coverage. For an example, FIGS. 9Aand 9B show the cross-section of a via contact for connection betweenmetal wiring. FIGS. 9A and 9B show a simple via contact and an anchorvia contact, respectively. The formation processes thereof are asfollows. A first metal layer 30 composed of aluminum (Al) is formed on asemiconductor substrate 20. A TiN film 40 is formed as a capping film onthe resultant structure by sputtering, and then an interlayer insulativefilm 50 or 51 is deposited. A contact hole is formed by etching theinterlayer insulative film 50 or 51 on the first metal layer 30. In FIG.9B, the step of forming an anchor A by wet etching is added. After Ti asan adhesive layer and TiN 60 or 61 as a barrier metal layer isdeposited, a tungsten (W) plug 70 or 71 is formed to fill the contacthole, by CVD. Thereafter, tungsten at the upper portion is removed bychemical mechanical polishing or etch-back, and then a second metallayer is deposited on the resultant structure, thereby completing theconnection between metal wiring. However, this last step is not shown.

Here, in a conventional method, the TiN film 60 or 61, being the barriermetal layer, is deposited by sputtering, with inferior step coverage.Here, the thickness of a TiN film on the bottom, corner and anchor A ofthe contact hole is reduced, with an increase in the aspect ratio of thevia. Accordingly, at a thin portion, Ti or Al combines with fluorineremaining in tungsten source gas WF₆ during tungsten deposition being asubsequent process, and thus an insulative film X is formed of TiF_(x)or ALF_(x), leading to a contact failure.

When the contact failure is avoided by increasing the deposition time toincrease the thickness of the TiN film 60 or 61, the thickness of theTiN film increases only at the upper portion of the contact hole, andthe upper portion of the contact hole is narrowed or blocked. Thus,voids are likely to be generated upon subsequent tungsten deposition. Aprocess with improved step coverage is required to apply TiN to acontact with a high aspect ratio. Accordingly, a process for fabricatinga metal nitride film using CVD (hereinafter called a CVD-metal nitridefilm) has been developed as a next generation process.

A general process for forming a CVD-metal nitride film uses a metalsource containing chlorine (Cl), e.g., a precursor such as titaniumchloride TiCl₄. The CVD-metal nitride film using TiCl₄ as the precursorhas a high step coverage of 95% or higher and is quickly deposited, butCl remains in the metal nitride film as impurities. The Cl remaining asimpurities in the metal nitride film causes corrosion of metal wiringsuch as Al and increases resistivity. Thus, the Cl content in the metalnitride film must be reduced and the resistivity must be lowered, bydeposition at high temperature. That is, in the CVD-metal nitride filmprocess using the metal source such as TiCl₄, a deposition temperatureof at least 675° C. is required to obtain resistivity of 200 μΩ-cm orless. However, a deposition temperature of 600° C. or more exceedsthermal budget and thermal stress limits which an underlayer canwithstand. In particular, when the metal nitride film is deposited on anSi contact or a via contact with an Al underlayer, a depositiontemperature of 480° C. or lower is required, so that a high temperatureCVD-metal nitride film process cannot be used.

A low temperature deposition CVD-metal nitride film process is possible,by adding MH (methylhydrazine, (CH₃)HNNH₂) to the metal source such asTiCl₄, but this method has a defect in that step coverage is decreasedto 70% or lower.

Another method capable of low temperature deposition is to form aMOCVD-metal nitride film using a metalorganic precursor such as TDEAT(tetrakis diethylamino Ti, Ti(N(CH₂CH₃)₂)₄), or TDMAT (tetrakisdimethylamino Ti, Ti(N(CH₃)₂)₄). The MOCVD-metal nitride film has noproblems due to Cl and can be deposited at low temperature. However, theMOCVD-metal nitride film contains a lot of carbon (C) as impurities,giving high resistivity, and has inferior step coverage of 70% or less.

A method of forming a metal nitride film using atomic layer epitaxy(ALE) has been tried as an alternative to deposition, in order toovercome the problems due to Cl. However, the ALE grows the metalnitride film in units of an atomic layer using only chemical absorption,and the deposition speed (0.25 A/cycle or less) is too slow to apply theALE to mass production.

A TiN film is also used as the electrode of a semiconductor capacitor.In particular, the TiN film is usually used in a capacitor which usestantalum oxide (Ta₂O₅) as a dielectric film. Semiconductor capacitors,which use the TiN film as an electrode, also have the above-describedproblems.

That is, in order for a semiconductor capacitor to have a highcapacitance per unit area of a semiconductor substrate, its electrode isdesigned three-dimensionally, as in cylindrical capacitors. Hence, theshape of the semiconductor capacitor is so complicated that it iscritical to guarantee step coverage of deposited materials as itselectrode. Accordingly, a TiN electrode formed by CVD using aCl-containing metal source having an excellent step coverage as aprecursor has been used as the electrode of a capacitor. However, asdescribed above, the CVDed TiN film provokes corrosion of metal wiringand gives high resistivity, due to a high concentration of Cl, resultingin a degradation in the leakage current characteristics of a capacitor.

SUMMARY OF THE INVENTION

To solve the above problems, an objective of the present invention is toprovide a method of forming a metal nitride film, which gives excellentstep coverage even at a high deposition speed and a low temperature, lowimpurity concentration, and low resistivity.

Another objective of the present invention is to provide a method offorming a metal contact having a barrier metal layer which has excellentstep coverage even at a high deposition speed and a low temperature, lowimpurity concentration, and low resistivity, by applying the metalnitride film formation method to a metal contact of a semiconductordevice.

Still another objective of the present invention is to provide a methodof forming a capacitor which gives excellent step coverage, low impurityconcentration and low resistivity, using the metal nitride filmformation method.

Accordingly, to achieve the first objective, there is provided a methodof forming a metal nitride film using chemical vapor deposition (CVD) inwhich a metal source and a nitrogen source are used as a precursor. Inthis method, first, a semiconductor substrate is introduced into adeposition chamber, and the metal source flows into the depositionchamber. After a predetermine time, the flow of the metal is stopped,and a purge gas is introduced into the deposition chamber. After apredetermined time, the purge gas is cut off and the nitrogen source gasflows into the deposition chamber to react with the metal sourceadsorbed on the semiconductor substrate. Again, after a predeterminedtime, the nitrogen source gas remaining in the deposition chamber isremoved by cutting off the inflow of the nitrogen source gas and flowingthe purge gas into the deposition chamber. Thus, the metal nitride filmis formed on the semiconductor substrate.

In the metal nitride film formation method of the present invention, agas inflow cycle of a sequence of the metal source, the purge gas, thenitrogen source, and the purge gas, can be repeated until a metalnitride film having a desired thickness is obtained.

Here, a titanium nitride film TiN can be formed by using TiCl₄ (titaniumchloride), TiCl₃ (titanium chloride), TiI₄ (titanium iodide), TiBr₂(titanium bromide), TiF₄ (titaniumfluoride), (C₅H₅)₂TiCl₂(bis(cyclopentadienyl)titanium dichloride), ((CH₃)₅C₅)₂TiCl₂(bis(pentamethylcyclopentadienyl) titanium dichloride), C₅H₅TiCl₃(cyclopentadienyltitanium trichloride), C₉H₁₀BCl₃N₆Ti (hydrotris(1-pyrazolylborato) trichloro titanium), C₉H₇TiCl₃ (indenyltitaniumtrichloride), (C₅(CH₃)₅)TiCl₃ (pentamethylcyclopentadienyltitaniumtrichloride), TiCl₄ (NH₃)₂ (tetrachlorodiaminotitanium),(CH₃)₅C₅Ti(CH₃)₃ (trimethylpentamethylcyclopentadienyltitanium), TDEATor TDMAT as the metal source, and using NH₃ as the nitrogen source.Alternatively, the tantalum nitride film TaN can be formed using amaterial selected from the group consisting of TaBr₅ (tantalum bromide),TaCl₅ (tantalum chloride), TaF₅ (tantalum fluoride), TaI₅ (Tantalumiodide), and(C₅(CH₃)₅)TaCl₄ (pentamethylcyclopentadienyltantalumtetrachloride), as the metal source, and using NH₃ as the nitrogensource.

Also, it is preferable that the purge gas is an inert gas such as Ar orN₂.

Preferably, 1-5 sccm of the metal source flows into the depositionchamber for 1 to 10 seconds, 5-200 sccm of the nitrogen source flowsthereinto for 1 to 10 seconds, and 10-200 sccm of the purge gas flowsthereinto for 1 to 10 seconds.

Also, an atmospheric gas such as Ar, He and N₂ can be continuouslyflowed into the deposition chamber, to maintain a constant pressure inthe deposition chamber.

Meanwhile, when the TiN film is formed using TDEAT or TDMAT as the metalsource, it is preferable to maintain the pressure in the depositionchamber to be 0.1-10 torr and the deposition temperature to be between250° C. and 400° C. When materials other than TDEAT and TDMAT are usedas the metal source, the pressure in the deposition chamber ismaintained to be 1 to 20 torr and the deposition temperature ismaintained to be between 400° C. and 500° C.

To achieve the second objective, there is provided a method of forming ametal contact of a semiconductor device, wherein a first metal layer, aninterlayer insulative film, a contact hole, a barrier metal layer, ametal plug, and a second metal layer are sequentially formed on asemiconductor substrate. A process for forming the barrier metal layeris as follows. A metal source flows into the semiconductor substratehaving the interlayer insulative film in which the contact hole exposingthe first metal layer is formed. The metal source is adsorbed to theresultant structure. After a while, the metal source remaining in thedeposition chamber is removed by cutting off the inflow of the metalsource and flowing a purge gas into the deposition chamber. After apredetermined time, the purge gas is cut off, and a nitrogen sourceflows into the deposition chamber. The nitrogen source reacts with themetal source adsorbed on the semiconductor substrate, to thus form ametal nitride film, being the barrier metal layer, on the exposed firstmetal layer and the contact hole. Again, after a while, the nitrogensource remaining in the deposition chamber is removed by cutting off theinflow of the nitrogen source and flowing the purge gas into thedeposition chamber.

The barrier metal layer formation process can be repeated until abarrier metal layer having a desired thickness is obtained.

Here, a titanium nitride film TiN as the barrier metal layer is formedby using a material selected from the group consisting of TiCl₄, TiCl₃,TiI₄, TiBr₂, TiF₄, (C₅H₅)₂TiCl₂, ((CH₃)₅C₅)₂TiCl₂, C₅H₅TiCl₃,C₉H₁₀BCl₃N₆Ti, C₉H₇TiCl₃, (C₅(CH₃)₅)TiCl₃, TiCl₄(NH₃)₂,(CH₃)₅C₅Ti(CH₃)₃, TDEAT and TDMAT as the metal source, and using NH₃ asthe nitrogen source. Alternatively, the tantalum nitride film TaN as thebarrier metal layer is formed using a material selected from the groupconsisting of TaBr₅, TaCl₅, TaF₅, TaI₅, and (C₅(CH₃)₅)TaCl₄ as the metalsource, and NH₃ as the nitrogen source.

Also, it is preferable that the purge gas is an inert gas such as Ar orN₂.

The flow amounts and flow times of the metal source, nitrogen source,and purge gas flowing into a deposition chamber are within the sameranges as in the above-mentioned method of forming the metal nitridefilm.

Also, in order to maintain a constant pressure within the depositionchamber while forming a barrier metal layer, the pressure within thedeposition chamber is kept at about 0.1 to 10 torr when TDEAT or TDMATis used as the metal source, and about 1 to 20 torr when materials otherthan TDEAT and TDMAT are used as the metal source. The constant pressureis maintained using an atmospheric gas such as Ar, He, or N₂.

It is preferable that a deposition temperature upon the formation of thebarrier metal layer is about between 250° C. and 400° C. when TDEAT orTDMAT is used as the metal source, and between 400° C. and 500° C. whenmaterials other than TDEAT and TDMAT are used as the metal source.

To achieve the third objective, there is provided a method of forming asemiconductor capacitor, wherein a lower conductive layer, a dielectricfilm and an upper conductive layer are sequentially formed on theunderlayer of a semiconductor substrate. In a process for forming thelower and/or upper conductive layer, a semiconductor substrate on whichan underlayer or a dielectric film is formed is introduced into adeposition chamber, and a metal source flows into the depositionchamber. The metal source is chemically and physically adsorbed onto thesubstrate. After a predetermined period of time, the metal source ispurged from the deposition chamber. After a predetermined period oftime, a nitrogen source flows into the deposition chamber, and ischemically and physically adsorbed onto the substrate. The adsorbedmetal source and nitrogen source are reacted to form a metal nitridefilm on the substrate. After another predetermined period of time, thenitrogen source is purged from the deposition chamber.

The step of forming a metal nitride film can be repeated until a lowerand/or upper conductive layer having a desired thickness is obtained.

Here, when Ti is used, the metal source used to form the lower and/orupper conductive layer is selected from the group consisting of TiCl₄,TiCl₃, TiI₄, TiBr₂, TiF₄, (C₅H₅)₂TiCl₂, ((CH₃)₅C₅)₂TiCl₂, C₅H₅TiCl₃,C₉H₁₀BCl₃N₆Ti, C₉H₇TiCl₃, (C₅(CH₃)₅)TiCl₃, TiCl₄(NH₃)₂,(CH₃)₅C₅Ti(CH₃)₃, TDEAT and TDMAT. When Ta is used, the metal source isselected from the group consisting of TaBr₅, TaCl₅, TaF₅, TaI₅, and(C₅(CH₃)₅)TaCl₄. The nitrogen source is NH₃.

Also, it is preferable that the purge gas is an inert gas such as Ar orN₂.

The flow amounts and inflow times of a metal source, a nitrogen sourceand a purge gas flowing into the deposition chamber are within the sameranges as those in the metal nitride film formation method according tothe present invention.

Also, in order to maintain a constant pressure within the depositionchamber while forming a lower and/or upper conductive layer, thepressure within the deposition chamber is maintained to be about 0.1-10torr when TDEAT or TDMAT is used as a metal source, and the pressurewithin the deposition chamber is maintained to be about 1-20 torr whenmaterials other than TDEAT and TDMAT are used as the metal source. Theconstant pressure is maintained by the use of an atmospheric gas such asAr, He or N₂.

Preferably, when TDEAT or TDMAT is used as the metal source, thedeposition temperature in each of the steps for forming a lowerconductive layer and/or an upper conductive layer is between 250° C. and500° C. Also, preferably, when other materials are used as the metalsource, the deposition temperature in each of the steps for forming alower conductive layer and/or an upper conductive layer is between 400°C. and 500° C.

According to the present invention, a metal nitride film having lowresistivity of 200μΩ-cm or less and a low content of Cl can be obtainedeven with excellent step coverage. Also, a CVD-metal nitride film can beformed at a temperature of 500° C. or less even at a deposition speed ofabout 20 A/cycle, so that the deposition speed of the present inventionis higher than that of a metal nitride film formation method using ALEhaving a growth speed of 0.25 A/cycle. A capacitor, in which a metalnitride film formed by the method according to the present invention isused as a lower and/or upper conductive layer, has excellent stepcoverage and excellent leakage current characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objectives and advantages of the present invention will becomemore apparent by describing in detail a preferred embodiment thereofwith reference to the attached drawings in which:

FIG. 1 shows a deposition chamber of a chemical vapor deposition (CVD)apparatus for depositing a metal nitride film on a semiconductorsubstrate, according to the present invention;

FIG. 2 shows gas inflow timings for depositing a metal nitride film on asemiconductor substrate, according to the present invention;

FIG. 3 is a graph of the results of Rutherford back scattering (RBS) ofa metal nitride film deposited according to the present invention;

FIG. 4 is a graph illustrating the resistivity and deposition speed of ametal nitride film with respect to flow amount of NH_(3,) when the metalnitride film is deposited according to the present invention;

FIG. 5 is a graph illustrating the resistivity and deposition speed of ametal nitride film with respect to pressure in a deposition chamber,when the metal nitride film is deposited according to the presentinvention;

FIG. 6 is a graph illustrating the deposited thickness of a metalnitride film versus the number of cycles when the metal nitride film isdeposited according to the present invention;

FIG. 7 is a graph illustrating the deposition speed of a metal nitridefilm versus the number of cycles when the metal nitride film isdeposited according to the present invention;

FIG. 8 is a graph illustrating the resistivity of a metal nitride filmversus deposition temperature when the metal nitride film is depositedaccording to the present invention;

FIGS. 9A and 9B are cross-sections of a via contact formed by aconventional method;

FIGS. 10A through 10F are cross-sectional views illustrating an exampleof a process for forming a via contact using the metal nitride filmformation method of the present invention;

FIGS. 11A through 11F are cross-sectional views illustrating anotherexample of a process for forming a via contact using the metal nitridefilm formation method of the present invention;

FIG. 12 is a graph illustrating the relationship between via resistivityand via width when a barrier metal layer is formed according to thepresent invention and the prior art;

FIG. 13 is a graph illustrating via resistivity distributions whenbarrier metal layers are formed according to the present invention andthe prior art;

FIGS. 14A through 14D are cross-sectional views illustrating a processfor forming a semiconductor capacitor using a metal nitride filmformation method according to the present invention;

FIGS. 15A and 15B are graphs showing the X-ray phonon spectroscopy (XPS)results of metal nitride films formed by a conventional method and amethod according to the present invention, respectively; and

FIG. 16 is a graph showing the leakage current characteristics ofcapacitors formed by a conventional method and a method according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a plurality of gas lines 114 a and 114 b forintroducing reaction gases into a deposition chamber 100 are installedinto the deposition chamber 100. Here, the number of gas lines dependson the number of metal sources and nitrogen sources, i.e., the number ofreaction gases, flowed into the deposition chamber 100. In an embodimentof the present invention, two gas lines 114 a and 114 b are installed.

The two gas lines 114 a and 114 b have one end connected to a supplysource (not shown) for a metal source and to a supply source (not shown)for a nitrogen source, respectively. When a TiN film is deposited on asemiconductor substrate 104, TiCl₄ is used as the metal source and NH₃is used as the nitrogen source. Meanwhile, the other ends of the gaslines 114 a and 114 b are connected to a shower head 110 isolated by apredetermined distance (D of FIG. 1) from the semiconductor substrate104 seated in the deposition chamber 100. Accordingly, the reactiongases from the gas supply sources (not shown) enter the depositionchamber 100 via the gas lines 114 a and 11 4 b and the shower head 110connected to the ends of the gas lines 114 a and 114 b. The reactiongases react with each other in the deposition chamber, and the resultantforms a film on the semiconductor substrate 104.

It is preferable that the shower head 110 is a multi-port shower headwhich allows the reaction gases to enter the deposition chamber 100 inan unmixed state. In this embodiment, a two-port shower head is used.Also, it is preferable that the gas lines 114 a and 114 b are providedwith purge gas supply lines 114 c and 114 d to supply to the depositionchamber 100 a purge gas for exhausting residual gases after reaction.

Valves 112 are installed on the respective gas supply lines. Accordingto the on/off state of the valves 112, the purge gases or reaction gasesmay enter into the deposition chamber 100 or be cut off. It ispreferable that the valves 112, such as pneumatic valves, are controlledby a programmed control unit to be periodically turned on or off.Reference numeral 102 is a heater for heating the semiconductorsubstrate 104.

A method of depositing a metal nitride such as TiN on a semiconductorsubstrate seated in the deposition chamber of a CVD apparatus havingsuch a configuration, according to the present invention, will now bedescribed in detail referring to FIGS. 1 and 2.

First, the semiconductor substrate 104 is introduced into the depositionchamber 100. The semiconductor substrate 104 may have devices such astransistors formed on its surface (see FIG. 1).

A metal source such as TiCl₄ flows into the deposition chamber 100 forthe time of t_(s) via the metal source supply line 114 a. Alternatively,the metal source can be mixed with a carrier gas such as Ar or N₂ toprovide a smooth gas flow into the deposition chamber 100. At this time,valves other than the valve of the gas supply line 114 a for supplying ametal source are in off state. Accordingly, only the metal source suchas TiCl₄ flows into the deposition chamber 100. At this time, a part ofthe entering metal source is chemically and physically adsorbed on thesurface of the substrate 104, and the residual remains in the depositionchamber 100. As described above, only one type of gas enters thedeposition chamber 100 for a predetermined time, instead ofsimultaneously flowing reaction gases into the deposition chamber 100.This is called gas pulsing (see FIG. 2).

When inflow of the metal source into the deposition chamber 100 iscompleted, the valve of the gas supply line 114 a for introducing themetal source is closed, and then the valve of the purge gas supply line114 c is opened to introduce the purge gas such as Ar or N₂ into thedeposition chamber 100 for the time of t_(p), thereby exhausting TiCl₄gases from the shower head 110 and the deposition chamber 100 (in thepurge gas pulsing step of FIG. 2). At this time, the flow of the purgegas and the pressure of the deposition chamber are appropriatelycontrolled to prevent the metal source chemically and physicallyadsorbed into the semiconductor substrate from being separated andexhausted, thereby exhausting only the source gas remaining within thedeposition chamber.

Then, the valve of the purge gas supply line 114 c is closed, and thevalve of the nitrogen gas source supply line 114 b is opened tointroduce a nitrogen gas such as NH₃ into the deposition chamber 100 fora time t_(r). The nitrogen gas reacts with the metal source such asTiCl₄ chemically and physically adsorbed into the substrate 104, thusforming the metal nitride such as TiN on the semiconductor substrate104. That is, because of the purge gas pulsing step before the nitrogensource such as NH₃ enters into the deposition chamber 100, the metalsource such as TiCl₄ remaining in the deposition chamber 100 isexhausted via the pump (see FIG. 1). Accordingly, the nitrogen sourcesuch as NH₃ does not react with the metal source such as TiCl₄ withinthe deposition chamber 100, except for on the semiconductor substrate104. Thus, the metal nitride is formed on only the semiconductorsubstrate 104 into which TiCl₄ and NH₃ are adsorbed (in the NH₃ pulsingstep of FIG. 2).

At this time, the carrier gas such as Ar or N₂ can be mixed with thenitrogen gas such as NH₃ for a smooth gas flow into the depositionchamber 100.

In a conventional method of forming a metal nitride film using ALE, onlythe chemically-adsorbed source remains, after purging the sourcephysically adsorbed on the substrate. On the other hand, in the metalnitride film formation method of the present invention, the sources bothphysically and chemically adsorbed on the substrate remain and react.This is the fundamental difference between the prior art and the presentinvention.

Next, the residual nitrogen source remaining within the depositionchamber 100 after the reaction with the metal source is exhausted byanother purge gas pulsing step (in the purge gas pulsing step of FIG.2).

Meanwhile, while the pressure in the deposition chamber 100 iscontrolled during the above-described steps, it is preferable that anatmospheric gas such as Ar or N₂ is continuously supplied into thedeposition chamber 100.

As described above, in the method of forming a metal nitride film usinggas pulsing, according to the present invention, the metal nitride filmsuch as TiN having a predetermined thickness is deposited through acycle having a sequence of the TiCl₄ pulsing step, the purge gas pulsingstep, the NH₃ pulsing step, and the purge gas pulsing step. Here, adeposition speed is about 20 A/cycle, and when this cycle is repeated,the thickness of a thin film is proportionally increased, so that a thinfilm having a desired thickness can be deposited on the semiconductorsubstrate 100. Here, the thickness of the metal nitride film depositedfor one cycle is determined by the flow amounts of the metal source andnitrogen source entering the deposition chamber 100, the gas pulsingtimes, the flow amount of the purge gas, and the purge time.

Hereinafter, experimental examples of forming a TiN film according tothe present invention will be described.

<First Experimental Example>

A TiN film is deposited by the cycles comprising the gas pulsing steps,under the following reaction conditions, on the semiconductor substrate104 which is maintained at a temperature of 500° C. or lower by theheater 102 of FIG. 1.

Deposition Conditions

object material: TiN

atmospheric gas: Ar

pressure in deposition chamber: 1-20Torr

metal source, nitrogen source: TiCl₄, NH₃

flow amount of TiCl₄, pulsing time (t_(s)) of TiCl₄:1-5 sccm, 5 sec

flow amount of NH₃, pulsing time (t_(r)) of NH₃: 5-30 sccm, 5 sec

purge gas, flow amount of purge gas, purge time (t_(p)): Ar, 10-100sccm, 10 sec

carrier gas, flow amount of carrier gas: Ar, 10-100 sccm

time (t_(t)) for one cycle: 30 sec

FIG. 3 shows the results of checking the state of the TiN thin filmdeposited on the semiconductor substrate 104 under the aforementionedconditions using an RBS method. In FIG. 3, a horizontal axis indicateschannels in a multi-channel analyzer (MCA), and a vertical axisindicates the standardized yields of elements detected by the MCA. Here,the relationship between each channel and energy is given by equation,E[eV]=4.05′ channel+59.4.

The TiN film deposited on the semiconductor substrate 104 under theaforementioned conditions has a unique gold color, and has a perfectcomposition of Ti:N=1:1 as shown in FIG. 3. Cl is 0.3% or less of thetotal elements contained in the TiN thin film, which is the detectionlimit by RBS, as shown in FIG. 3. Also, the resistivity of the TiN filmdeposited on the semiconductor substrate 104 under the above conditionswas measured as a low value of about 130 μΩ-cm. Meanwhile, according toseveral experiments, it was verified that the thickness of the TiN thinfilm deposited for each cycle must be 20 A or less to provide such anexcellent thin film property.

FIGS. 4 and 5 show the resistivity and deposition speed of the TiN filmdeposited according to the present invention, at various flow amounts ofthe nitrogen source NH₃ and pressures in the deposition chamber,respectively. As shown in FIGS. 4 and 5, the deposition speed increaseswith an increase in the flow amount of NH₃ and the pressure in thedeposition chamber, and thus the resistivity also increases.Accordingly, it is preferable that the conditions for deposition are setin consideration of the thickness and the deposition speed andresistivity of the metal nitride film required according to places toapply the metal nitride film.

<Second Experimental Example>

A deposition speed for each cycle, the thickness and deposition speed ofa TiN film deposited according to an increase in the number of cycles,and resistivity according to a change in deposition temperature, aremeasured under four deposition conditions as shown in the followingTable 1. Here, the metal source is TiCl₄, the nitrogen source is NH₃,and the purge gas is Ar.

TABLE 1 amount amount amount and amount amount of deposition and timeand time time of and time atmospheric conditions of metal source ofpurge gas nitrogen source of purge gas pressure gas TiN 00 5 sccm, 40sccm, 150 sccm, 40 sccm, 3 torr 50 sccm 5 sec 5 sec 5 sec 5 sec TiN 01 3sccm, 150 sccm, 30 sccm, 150 sccm, 2 torr 30 sccm 3 sec 3 sec 3 sec 3sec TiN 02 3 sccm, 150 sccm, 50 sccm, 150 sccm, 3 torr 30 sccm 2 sec 2sec 2 sec 2 sec TiN 03 3 sccm, 150 sccm, 100 sccm, 150 sccm, 3 torr 30sccm 2 sec 2 sec 2 sec 2 sec

Deposition speeds per cycle under the above deposition conditions are asfollows:

TiN 00:20 A/cycle (60 A/min, since one cycle is 20 seconds)

TiN 01:2 A/cycle (10 A/min, since one cycle is 12 seconds)

TiN 02:3.5 A/cycle (26.3 A/min, since one cycle is 8 seconds)

TiN 03:6 A/cycle (45 A/min, since one cycle is 8 seconds).

FIGS. 6 and 7 show the deposition thickness and deposition speed,respectively, according to an increase in the number of cycles. Here, adeposition temperature is 500° C. As can be seen from FIGS. 6 and 7, thedeposition speed increases slowly with an increase in the number ofcycles, and the deposition thickness increases in proportion to thenumber of cycles. Thus, the thickness of the TiN film to be depositedcan be controlled by adjusting the number of cycles under consistentdeposition conditions.

FIG. 8 is a graph showing resistivity of the TiN film with respect todeposition temperature according to the four deposition conditionsdescribed above. It can be seen from FIG. 8 that the resistivitydecreases with an increase in the deposition temperature. Particularly,it can be seen that the resistivity sharply decreases under thedeposition condition (TiN 00) in which the deposition speed is high.Also, we can recognize that resistivity of 200μΩ-cm or less is obtainedat about 500° C. under all the four deposition conditions.

An example of applying the metal nitride film formation method of thepresent invention to a via contact will now be described in detail,referring to FIGS. 10A through 11F.

First, a first metal layer 210 such as Al is formed on a semiconductorsubstrate 200, and a TiN film 220 is deposited as a capping film on theresultant structure, as shown in FIG. 10A. The TiN film 220 can bedeposited by sputtering. Then, an interlayer insulative film 230 isdeposited, and a portion on which a via is to be formed is etched,thereby forming the structure of FIG. 10B. A thin Ti film (not shown) isformed on the resultant structure to improve attachment strength of theTiN film, before the TiN film, being a barrier metal layer, isdeposited. This Ti film can also be formed by sputtering.

Next, the TiN film 240, being a barrier metal layer, is deposited by themetal nitride film formation method of the present invention, thusforming the structure of FIG. 10C. That is, as described above, a metalsource, a purge gas, and a nitrogen source flow into the depositionapparatus of FIG. 1 in the sequence of the metal source, the purge gas,the nitrogen source, and the purge gas. This is repeated until a desiredthickness is obtained. Here, the metal source is TiCl₄ and the nitrogensource is NH₃. The amounts of the metal source, the nitrogen source andthe purge gas are 1 to 5 sccm, 5 to 200 sccm, and 10 to 200 sccm,respectively, and the inflow times thereof are about 1 to 10 seconds. Adeposition temperature is 480° C. or lower, and the pressure in thedeposition chamber is between 1 torr and 20 torr. If necessary, anatmospheric gas such as Ar, He, or N₂, and a carrier gas of Ar, N₂,etc., can be used. These deposition conditions are appropriatelycontrolled considering the deposition apparatus, the deposition speed,the thickness of the TiN film deposited, and the resistivity of the TiNfilm.

A metal plug 250 such as W is formed by a typical method, in FIG. 10D,and a metal deposited on the upper surface of an interlayer insulativefilm 230 is removed by chemical mechanical polishing or etch back, inFIG. 10E. Then, when a second metal layer 260 is formed on the resultantstructure as shown in FIG. 10F, interconnection between metal layers isaccomplished.

FIGS. 11A through 11F are cross-sectional views illustrating a processfor forming an anchor via contact, which is fundamentally the same asthe process of FIGS. 10A through 10F except that an anchor A is formedon the lower portion of a contact hole to lower resistance by increasinga contact area as shown in FIG. 11B. The anchor A is formed by wetetching the interlayer insulative film 335 after forming the contacthole as shown in FIG. 11A. The other steps are the same as those ofFIGS. 10A through 10F, so they will not be described again.

As described above, when the metal nitride film formation method of thepresent invention is applied to the via contact, a barrier metal layerhaving an excellent step coverage can be obtained at low temperature.Thus, a contact failure X such as TiFx or AlFx shown in FIGS. 9A and 9Bcan be prevented.

<Third Experimental Example>

A Ti film is deposited to a thickness of 100A on contact holes ofvarious different widths, by sputtering. Then, as a barrier metal layer,a TiN film according to the present invention, and a collimated TiN filmformed by sputtering by a conventional method, are deposited todifferent thicknesses, and a plug is formed of CVD-W. The thirdexperiment measures via resistance in this case. Here, the depositionconditions of the TiN film according to the present invention are equalto the deposition conditions of TiN 00 of the aforementioned secondexperiment, with a deposition temperature of 450° C.

Via widths: 0.24 μm, 0.32 μm, 0.39 μm (via depth: 0.9 μm)

Thickness of TiN film: 100 A, 200 A, 400 A, 600 A (these are depositedby the method of the present invention), 700 A (collimated TiN film)

As the results of measurement, resistivity generally decreases with anincrease in via width as shown in FIG. 12, and resistivity decreaseswith decreasing the thickness of the TiN film of the present invention.The 100 A-thick TiN film according to the present invention has asimilar resistance to the collimated TiN film. In particular, when thevia width is 0.39 μm, the above five TiN films have similar viaresistances. Meanwhile, in the second experiment and as shown in FIG. 8,the TiN films of the present invention were formed at a high depositionspeed per cycle (20 A/cycle) and with large resistivity (300μΩ-cm at450° C.). Accordingly, if the TiN films of the present invention areformed at a lower deposition speed and with smaller resistivity, theirvia resistances can be significantly improved.

FIG. 13 is a graph showing the distribution of the via resistance ofeach TiN film when the via width is 0.39 μm. From the graph of FIG. 13,we can recognize that the collimated TiN film and the TiN filmsaccording to the present invention are evenly distributed, without a bigdifference, around 1.0Ω.

Up to now, the present invention has been described by taking as anexample the method wherein the TiN film is formed as a metal nitridefilm by using TiCl₄ and NH₃ as a precursor. However, the presentinvention can be applied to a TiN film using TiCl₃, TiI₄, TiBr₂, TiF₄,(C₅H₅)₂TiCl₂, ((CH₃)₅C₅)₂TiCl₂, C₅H₅TiCl₃, C₉H₁₀BCl₃N₆Ti, C₉H₇TiCl₃,(C₅(CH₃)₅)TiCl₃, TiCl₄(NH₃)₂, (CH₃)₅C₅Ti(CH₃)₃, TDEAT or TDMAT insteadof TiCl₄ as the precursor, and also to other metal nitride films such asTaN firm using TaBr₅, TaCl₅, TaF₅, TaI_(5,) or (C₅(CH₃)₅)TaCl₄ asprecursors, and further to almost any material layers deposited usingCVD.

However, when the TiN film is formed using TDEAT or TDMAT as theprecursor, it is preferable that a deposition temperature is between250° C. and 400° C. and a pressure is about 0.1 to 10 torr, in contrastwith the cases using the other materials as the precursor. Since theabove precursors for forming the TaN film are all solid, a solid bubblermust be used to form a source gas.

An example of forming a semiconductor capacitor by applying the metalnitride formation method according to the present invention to acapacitor electrode will now be described in detail with reference toFIGS. 14 through 16.

A semiconductor capacitor is formed by sequentially stacking a lowerconductive layer, a dielectric film and an upper conductive layer. Theprocess for forming a lower and/or upper conductive layer to form asemiconductor capacitor according to the present invention adopts themetal nitride film formation method according to the present inventiondescribed above. That is, as described above, a metal source, a purgegas, and a nitrogen source flow into the deposition apparatus of FIG. 1in the sequence of the metal source, the purge gas, the nitrogen source,and the purge gas. This is repeated until a desired thickness isobtained. Here, the metal source is TiCl₄ and the nitrogen source isNH₃. The amounts of the metal source, the nitrogen source and the purgegas are 1 to 5 sccm, 5 to 200 sccm, and 10 to 200 sccm, respectively,and the inflow times thereof are about 1 to 10 seconds. A depositiontemperature is 480° C. or lower, and the pressure in the depositionchamber is between 1 torr and 20 torr. If necessary, an atmospheric gassuch as Ar, He, or N₂, and a carrier gas of Ar, N₂, etc., can be used.These deposition conditions are appropriately controlled considering thedeposition apparatus, the deposition speed, the thickness of the TiNfilm deposited, and the resistivity of the TiN film.

Up to now, the present invention has been described by taking as anexample the method wherein the TiN film is formed as a metal nitridefilm by using TiCl₄ and NH₃ as a precursor. However, TiCl₃, TiI₄, TiBr₂,TiF₄, (C₅H₅)₂TiCl₂, ((CH₃)₅C₅)₂TiCl₂, C₅H₅TiCl₃, C₉H₁₀BCl₃N₆Ti,C₉H₇TiCl₃, (C₅(CH₃)₅)TiCl₃, TiCl₄(NH₃)₂, (CH₃)₅C₅Ti(CH₃)₃, TDEAT orTDMAT can be used as the precursor. In case that a TaN film is formed asa metal nitride film, TaBr₅, TaCl₅, TaF₅, TaI₅, or (C₅(CH₃)₅)TaCl₄ canbe used as precursors.

When the TiN film is formed using TDEAT or TDMAT as the precursor, it ispreferable that a deposition temperature is between 250° C. and 400° C.and a pressure is about 0.1 to 10 torr. Since the above precursors forforming the TaN film are all solid, a solid bubbler must be used to forma source gas.

<Fourth Experimental Example>

FIGS. 14A through 14D are cross-sectional views illustrating a processfor forming a semiconductor capacitor having a cylindrical electrodestructure for measuring step coverage and leakage currentcharacteristics. Referring to FIG. 14A, an SiO₂ sacrificial oxide film440 is formed on a semiconductor substrate 400 on which a predeterminedcontact 420 and an etch stop film 430 are formed. The contact 420electrically connects the active region of the semiconductor substrateto the electrode of a capacitor via the interlayer dielectric film 410.

Referring to FIG. 14B, cylindrical holes 447 are formed by dry etchingthe sacrificial oxide film 440, and then a lower conductive layer 450 isformed by chemical vapor depositing polysilicon. Continuously, as shownin FIG. 14C, a lower electrode 455 is formed by node separating thelower conductive layer 450, and then the sacrificial oxide film 440 ofFIG. 14B remaining between the lower electrodes 455 is removed. Next, asshown in FIG. 14D, a dielectric film 460 is formed by chemical vapordepositing Ta₂O₅ on the semiconductor substrate on which the lowerelectrode has been formed, and an upper conductive layer is formed onthe dielectric film at about 480° C. using TiCl₄ nitrogen precursor andan NH₃ nitrogen source by the metal nitride film formation methodaccording to the present invention. Thereafter, a polysilicon film isformed on the upper conductive layer, thereby forming the structure of acapacitor according to the present invention. A conventional capacitoris formed by the same method as the above-described method by which thecapacitor according to the present invention is formed, except that anupper conductive layer is formed by chemical vapor depositing a TiN filmat about 620° C. using TiCl₄ and NH₃ as a source gas. Here, 10 sccm ofTiCl₄ and 50 sccm of NH₃ are used when TiN is chemical vapor deposited.

As to the capacitor formed by a method according to the presentinvention (expressed as SLD-TiN) and the capacitor having a chemicallyvapor deposited (CVDed) TiN upper conductive layer (expressed asCVD-TiN), the step coverage of an upper conductive layer and the leakagecurrent characteristics are measured and shown in Table 2 and FIG. 16,respectively.

TABLE 2 Classification Lower thickness Upper thickness Step coverageCVD-TiN  35A 156A 22.6% SLD-TiN 188A 208A 90.1%

In Table 2, the upper and lower thicknesses denote the thicknesses of anupper conductive layer at portions pointed by reference characters t₁and t₂ shown in FIG. 14D, respectively. As can be seen from Table 2, thestep coverage of the capacitor according to the present invention issignificantly higher than that of the capacitor having a CVD'ed TiNupper conductive layer. The CVD technique can also improve step coverageby increasing the flow ratio of TiCl₄/NH₃, but has a drawback in thatthe leakage current characteristics is degraded due to an increase inthe concentration of Cl remaining within a film.

In FIG. 16, the leakage current value of the capacitor according to thepresent invention (SLD-TiN) is lower than that of the capacitor having aCVDed upper conductive layer (CVD-TiN) in most of an applied voltagesection. In particular, around ±1.2 V, which is the basis of the leakagecurrent characteristics of a capacitor, the leakage current value of thecapacitor according to the present invention is only about ⅓ or{fraction (1/15)} times that of the capacitor having a CVDed upperconductive layer.

FIGS. 15A and 15B show the content of Cl contained in a conductive layerformed by a method according to the present invention and the content ofCl contained in a CVDed conductive layer, respectively. The measurementof the Cl content is achieved by performing XPS with respect to a TiNfilm formed by the metal nitride film formation method according to thepresent invention and a CVDed TiN film which are separately formed onSiO₂ substrates. In the graphs of FIGS. 15A and 15B, the left portioncorresponds to a TiN film region, and the right portion, where etchingis further progressed, corresponds to an SiO₂ substrate region. As shownin FIGS. 15A and 15B, the Cl content of the TiN film formed by a methodaccording to the present invention is a maximum of 0.4 atomic % in theTiN film region, but the Cl content of the TiN film formed by CVD is amaximum of 3.9 atomic % in the TiN film region. Preferably, the Clcontent in a general capacitor is maintained below 1%. Thus, it can beseen that the TiN film formed by a method according to the presentinvention has a Cl content that is suitable for the conductive layer ofa semiconductor capacitor.

According to the metal nitride film fonnation method of the presentinvention as described above, a metal nitride film has low resistivityof 200μΩ-cm or less even with excellent step coverage and contains onlya small amount of Cl. Also, the metal nitride film can be formed at atemperature of 500° C. or lower, and also a deposition speed,approximately 20 A/cycle, is considerably higher than that in the metalnitride film formation method using ALE with a growth speed of 0.25A/cycle.

Accordingly, as opposed to when a metal nitride film is deposited at atemperature of 650° C. or higher in a conventional method, corrosion ofmetal wiring and high resistivity due to impurities (Cl) remaining inthe metal nitride film can be solved, so that the present invention isapplicable to a via contact which has a high aspect ratio and requires alow temperature. Also, since the present invention has a higherdeposition speed than the metal nitride film formation method using ALE,it is suitable for mass production.

Also, the metal nitride film formation method according to the presentinvention can be used to form the electrode of a semiconductor capacitorhaving a three-dimensional electrode structure, leading to the formationof a semiconductor capacitor having a very low content of Cl andexcellent leakage current characteristics.

What is claimed is:
 1. A method of forming a semiconductor capacitor bysequentially forming a lower conductive layer, a dielectric film and anupper conductive layer on the underlayer of a semiconductor substrate,wherein the process for forming a lower conductive layer and/or an upperconductive layer comprises the steps of: (a) inserting a semiconductorsubstrate on which the underlayer on the dielectric film is formed, intoa deposition chamber; (b) admitting a metal source into the depositionchamber (c) chemisorbing a first portion of the metal source onto thesubstrate, and physisorbing a second portion of the metal source ontothe substrate; (d) purging the metal source from the deposition chamber;(e) admitting a nitrogen source into the deposition chamber; (f)chemisorbing a first portion of the nitrogen source onto the substrate,and physisorbing a second portion of the nitrogen source onto thesubstrate; (g) reacting the chemisorbed and physisorbed metal sourcewith the chemisorbed and physisorbed nitrogen source to form a metalnitride film on the substrate; and (h) purging the nitrogen source fromthe deposition chamber.
 2. The method as claimed in claim 1, wherein themetal source is selected from the group consisting of TiCl₄, TiCl₃,TiI₄, TiBr₂, TiF₄, (C₅H₅)₂TiCl₂, ((CH₃)₅C₅)₂TiCl₂, C₅H₅TiCl₃,C₉H₁₀BCl₃N₆Ti, C₉H₇TiCl₃, (C₅(CH₃)₅)TiCl₃, TiCl₄(NH₃)₂, and(CH₃)₅C₅Ti(CH₃)₃, and the nitrogen source is NH₃.
 3. The method asclaimed in claim 2, wherein the deposition temperature in the steps (b)through (h) is between 400° C. and 500° C., and the pressure in thedeposition chamber is 1 to 20 torr.
 4. The method as claimed in claim 1,wherein TDEAT or TDMAT is used as the metal source, and NH₃ is used asthe nitrogen source.
 5. The method as claimed in claim 4, wherein thedeposition temperature in the steps (b) through (h) is between 250° C.and 400° C. and the pressure in the deposition chamber is 0.1 to 10torr.
 6. The method as claimed in claim 1, wherein a material selectedfrom the group consisting of TaBr₅, TaCl₅, TaF₅, TaI₅,and(C₅(CH₃)₅)TaCl₄ is used as the metal source, and NH₃ is used as thenitrogen source.
 7. The method as claimed in claim 6, wherein thedeposition temperature in the steps (b) through (h) is between 400° C.and 500° C., and the pressure in the deposition chamber is 1 to 20torr.8. The method as claimed in claim 1, wherein the purge gas is Ar or N₂.9. The method as claimed in claim 1, wherein 1-5 sccm of the metalsource flows into the deposition chamber for 1 to 10 seconds, 5-200 sccmof the nitrogen source flows thereinto for 1 to 10 seconds, and 10-200sccm of the purge gas flows thereinto for 1 to 10 seconds.
 10. Themethod as claimed in claim 1, wherein an atmospheric gas, which is atleast one selected from the group consisting of Ar, He and N₂, iscontinuously flowed into the deposition chamber during the steps (b)through (h), to maintain a constant pressure in the deposition chamber.11. The method as claimed in claim 1, wherein the thickness of the lowerand/or upper conductive layer is controlled by repeating the steps (b)through (h).